The present invention relates to a recycling cooking oven, and more particularly to a recycling cooking oven having a catalytic converter.
U.S. Pat. Nos. 5,254,823; 5,434,390; and 5,558,793 describe a recycling cooking oven which provides a substantially closed environment. Recycling cooking ovens typically utilize hot air to supply the heat energy for hot air impingement cooking. In a "hybrid" recycling cooking oven, both hot air and microwaves (from magnetrons) supply the energy for cooking. Such recycling cooking ovens are highly economical as the substantially closed environment means that the heat produced for the purposes of cooking is not needlessly vented to the atmosphere outside of the oven, but is used substantially exclusively for its intended purpose of cooking. Nonetheless, a combination of the inevitable heat losses from the oven to the ambient atmosphere (either through the oven walls or through the opening and closing of the cooking chamber door) plus the heat energy which is removed as part of the cooked foods taken out of the cooking chamber must be compensated for in some manner, traditionally at a substantial cost. Through proper insulation of the oven and careful design of the doorway through which food is introduced into and removed from the cooking chamber of the oven, these inevitable thermal losses may be minimized. However, recycling ovens are subject to unique problems not encountered, or only minimally encountered, in non-recycling ovens.
In a recycling oven, the hot air which moves over and around the food in the cooking chamber tends to carry with it small food particles which have become detached from the food as well as airborne grease and other particulates which have been created or released by the cooking process. The maintenance of clean cooking air (and, of course, a clean oven) is important for both sanitation and high quality food as well as to maximize the operating efficiency of the oven's cooking operation. For example the operating efficiency of the magnetrons used in microwave cooking is particularly sensitive to the cleanliness of the cooking air. Preferably the recycling oven is capable of cooking a wide variety of foods and is capable of replicating cooking methods ranging from broiling, baking, poaching and frying to roasting, toasting, steaming and grilling, etc. Especially when the oven is cooking partially cooked or raw meats, a large quantity of airborne greases are introduced into the cooking chamber and hence the cooking air. As a result, there may be a transfer of flavor between different foods which are being cooked in the same cooking chamber either simultaneously (whether or not the oven is a recycling one) or successively (i.e., in successive cooks of a recycling oven).
A conventional commercial oven (whether recycling or not) utilizes various methods to clear the air for re-use and to reduce the amount of airborne particles which would otherwise be deposited on the internal cooking surfaces of the cooking chamber and/or on the food items being cooked at that time or in subsequent cooking operations. The first method is a catch basket at the bottom of the cooking chamber which captures any large particles of food which break off during the cooking operation. The particles are held in the basket by gravity for easy removal during the daily cleaning operation. The second method is a metal filter screen through which all of the air which has been used in the cooking operation passes before it can be returned to the cooking chamber in a recycling oven or vented in a non-recycling oven. The metal filter screen mechanically removes airborne particles, including larger particles of grease, and deposits these impurities in a catch pan located beneath the filter screen. Both the filter screen and the catch pan can easily be removed from the oven for cleaning during the daily cleaning operation. The third method is the daily cleaning operation itself whereby all of the elements of the cooking chamber which come in contact with the air used in the cooking operation are cleaned in a prescribed manual operation.
Nonetheless, even the combination of these air clearing techniques has not proven to be entirely satisfactory. Accordingly, current commercial ovens--even the recycling ones--are frequently used in conjunction with an overhead hood ventilation system to capture and ventilate any amounts of airborne grease which are discharged by the oven in high-grease operations. Many municipalities and their regulatory agencies require these types of overhead ventilation systems to assure the safety of the cooking operation (as accumulated deposits of grease can be a fire hazard) and the quality of the food cooked. Most of these types of overhead ventilation systems are permanent installations, which are both costly and cumbersome.
Currently the fastest-growing segment of the "fast food" industry is the so-called "non-traditional" site. Many of the large national chains have exhausted the availability of high-traffic real estate sites for either free-standing buildings or in-line storefront locations. In addition, as real estate has become more expensive on a square foot basis, the pressure to shrink the size of restaurant kitchens has been intense. Nowhere is this more true than in the "non-traditional" location where total operating space is reduced from an average of 2000-40000 square feet to 400-800 square feet. These non-traditional locations are often within larger buildings such as airports, mass merchandisers, and convenience stores, where access to outside ventilation is even more expensive than in a traditional restaurant site. Clearly, the need is great for an advanced air clearing system which obviates the necessity for an overhead hood ventilation system.
Accordingly, it is an object of the present invention to provide a recycling oven which requires the addition of only a minimum of heat energy for continued cooking operation.
Another object is to provide such an oven wherein there is a minimum of flavor and odor transfer between the different foods in simultaneous or consecutive cooks.
A further object is to provide such an oven which does not require an overhead hood ventilation system.
It is also an object to provide such an oven which requires a minimum of manual labor during the daily cleaning operation.